When we think of computers today, we imagine slim laptops and powerful smartphones. However, the story of ENIAC, the world’s very first general-purpose computer, tells of an enormous, room-sized machine that laid the foundation for all modern computing. The story of ENIAC is filled with brilliant minds, groundbreaking innovation, and incredible ambition.
The visionaries behind the story of ENIAC
The Electronic Numerical Integrator and Computer, or ENIAC, was the brainchild of two remarkable American engineers: John Presper Eckert and John William Mauchly. In 1943, they proposed building an electronic computer to the United States Army during World War II, aiming to solve complex ballistic calculations much faster than human “computers” could.
At that time, Mauchly was a professor of physics at Ursinus College in Pennsylvania, and Eckert was an electrical engineering student at the University of Pennsylvania’s Moore School of Electrical Engineering. Their collaboration became the spark for a technological revolution.
The United States Army Ballistic Research Laboratory, based at Aberdeen Proving Ground in Maryland, recognised the critical need for faster computation. In June 1943, the Army approved the ENIAC project, granting an initial budget of $61,700, a substantial sum during the wartime economy.
Building a giant: where and how the story of ENIAC was constructed
The story of ENIAC continued at the Moore School of the University of Pennsylvania in Philadelphia, where construction began during World War II. A team of engineers and workers raced against time to build the machine.
The final machine was completed in February 1946, after approximately 200,000 man-hours of work. Its physical specifications were staggering:
- Size: roughly 30 metres (98 feet) long and 2.4 metres (8 feet) high.
- Weight: about 27 tonnes (60,000 pounds).
- Components: included 18,000 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, and 10,000 capacitors.
- Power Consumption: approximately 150 kilowatts — enough to light up a small town at the time.
The machine was so large that it occupied 1,800 square feet (167 square metres) — roughly the size of a small house.
Interestingly, it was rumoured that when ENIAC was switched on, the lights of Philadelphia would flicker due to its enormous electricity draw. While this was a myth, it highlights the legendary status ENIAC quickly achieved even among the public.
Challenges during construction
Building ENIAC was no easy feat. The team faced countless technical obstacles. Vacuum tubes were delicate and burned out frequently. It was expected that ENIAC would constantly suffer downtime due to tube failures.
Surprisingly, because the system was left running continuously (and thus avoided the damaging temperature changes from power cycling), ENIAC operated more reliably than anticipated. It typically had one tube failure every two days — a far better record than engineers had dared hope.
The unsung heroes: the first programmers
While Eckert and Mauchly designed ENIAC, the first programmers were six brilliant women: Jean Jennings Bartik, Kathleen McNulty, Frances Bilas, Betty Snyder, Marlyn Wescoff, and Ruth Lichterman. They manually configured ENIAC by setting switches and connecting hundreds of cables to direct the machine’s operations.
Their pioneering work, performed largely without detailed blueprints or prior examples, laid the groundwork for modern programming. For many years, their contributions were overlooked in historical accounts, but today, their role is widely recognised and celebrated.
ENIAC’s first job
The first calculations completed by ENIAC were to produce artillery firing tables for the U.S. Army’s Ballistic Research Laboratory. This task was critical for accurately aiming artillery during wartime.
One of ENIAC’s first major public demonstrations involved calculating the trajectory of a shell, taking about 30 seconds — a task that had previously taken several hours by hand.
Its successful demonstration in February 1946 at the Moore School stunned observers, leading the media to hail ENIAC as a “Giant Brain.”
How the story of ENIAC continued and its incredible legacy
How ENIAC processed information
Unlike modern digital computers, ENIAC used decimal numbers, not binary. It performed calculations using a series of ten vacuum tubes for each digit, which made its structure both complex and fascinating.
The machine included:
- Twenty accumulators, each capable of storing a ten-digit decimal number.
- A high-speed multiplier, which could perform 300 multiplications per second.
- A divider and square rooter, operating at about 50 divisions per second.
- Three function tables, each able to store 104 values.
Programming ENIAC was incredibly labour-intensive. To change a program, operators had to physically rewire the machine and adjust hundreds of switches. A reprogramming task could take anywhere from a few hours to several days.
ENIAC’s incredible performance
At its peak, ENIAC could perform 5,000 additions, 357 multiplications, or 38 divisions per second — speeds unimaginable at the time. Compared to previous manual methods, ENIAC was up to 1,000 times faster.
It completed calculations that had previously taken days or weeks by hand in mere hours. This leap in speed marked the beginning of the digital age.
Fun facts about the story of ENIAC
- ENIAC’s total cost was about $487,000 — equivalent to roughly $7 million today.
- The entire system included over 5 million hand-soldered joints.
- Despite using vacuum tubes, ENIAC was more reliable than anticipated due to continuous operation.
- It could be reprogrammed to perform entirely different tasks — a groundbreaking feature for its time.
- ENIAC’s panels were later moved and displayed at the Smithsonian Institution and the University of Pennsylvania.
Key specifications and features of ENIAC
| Parameter | Details |
|---|---|
| Full Name | Electronic Numerical Integrator and Computer |
| Creators | John Presper Eckert and John William Mauchly |
| Built at | Moore School of Electrical Engineering, University of Pennsylvania |
| City | Philadelphia, USA |
| Year Completed | February 1946 |
| Size | 30 metres long, 2.4 metres high |
| Weight | 27 tonnes (60,000 pounds) |
| Components | 18,000 vacuum tubes, 7,200 diodes, 1,500 relays |
| Power Consumption | 150 kilowatts |
| Speed | 5,000 additions, 357 multiplications, or 38 divisions per second |
| First Use | Artillery trajectory calculations for the U.S. Army |
| Legacy | Inspired stored-program architecture and modern computing |
The transition to stored programs
While ENIAC was revolutionary, it had one major limitation: it could not store programs internally. The next leap came with the EDVAC (Electronic Discrete Variable Automatic Computer), designed by the same team but based on the concept of stored programs, an idea proposed by John von Neumann.
Von Neumann’s “First Draft of a Report on the EDVAC” (1945) laid the theoretical foundation for virtually every modern computer built since.
ENIAC’s enduring legacy
The story of ENIAC not only revolutionised military computation but also inspired advances in weather prediction, atomic energy calculations, and early business computing. It paved the way for companies like IBM to enter the computing industry.
Without ENIAC, our world of smartphones, AI, and cloud computing might have looked very different.
Today, ENIAC remains a powerful symbol of human ingenuity, perseverance, and the relentless pursuit of progress.
Thus, the story of ENIAC is not just about circuits and wires. It is the story of how humanity first taught a machine to think.
